1. Field of the Invention
The present invention relates to a waterproof method for a wire end joint portion of a wiring harness to be installed in an automotive vehicle and a waterproof construction formed by this method and, more particularly, is designed to easily and reliably apply waterproofing to a wire end joint portion, which is formed by integrally welding exposed parts of cores at the ends of a plurality of wires, using a general-purpose tube instead of applying waterproofing by protecting the wire end joint portion by means of a special protection cap.
2. Description of the Related Art
Conventionally, in the case of connecting wires of a wiring harness to be installed in an automotive vehicle, insulation coatings are stripped at ends or intermediate portions of the wires to expose cores and exposed parts of the cores are connected by welding, soldering or crimp connection by a crimping terminal.
There are many cases where a protection cap made of resin is mounted on a wire end joint portion (end connecting spliced portion) formed by connecting cores at ends of a plurality of wires as above for the insulation protection. In a wiring harness to be installed in an engine compartment, which is a water exposed area, waterproofing is applied by filling a waterproofing agent 2 in the protection cap.
Specifically, after a specified amount of the waterproofing agent 2 is injected into a cap 1 by an injector (not shown) as shown in FIG. 5, a wire end joint portion Y of a wire group W is inserted into the cap 1 and the waterproofing agent 2 is solidified to seal the wire end joint portion Y for the waterproofing purpose.
However, the cap 1 is required to have a sufficiently large inner diameter due to the capability of the injector upon injecting the waterproofing agent into the cap 1. Further, the specifications of wire end joint portions Y largely differ and, hence, caps 1 capable of dealing with various sizes need to be used. This necessitates many kinds of caps, leading to a cost increase for mold production and consequently leading to a higher cost.
Further, in the case of using a cap selected from those prepared beforehand, the outer diameter of the cap is larger than the wire end joint portion Y, thereby presenting a problem of deteriorating space efficiency.
Particularly, in the case of accommodating the wire end joint portion Y into a corrugated tube, a corrugated tube having a large inner diameter needs to be used, therefore leading to increases of cost and necessary space. Further, if the inner diameter of the cap 1 increases, the amount of the waterproofing agent 2 to be injected also increases, leading to a cost increase also for the waterproofing agent 2.
In Japanese Unexamined Patent Publication No. H11-178142, a heat shrinkable tube 4 having a hot melt adhesive 3 applied to the inner wall thereof and having an opening at one end sealed by a hot melt agent 3′ as shown in FIG. 6 is provided, a wire end joint portion Y is inserted into the heat shrinkable tube 4, and a clearance is filled up by melting the hot melt adhesive 3 simultaneously with the heat shrinkage of the heat shrinkable tube 4, thereby sealing the wire end joint portion Y.
However, there is a high possibility that the hot melt agent 3′ used as a sealing member is also melted upon heating the heat shrinkable tube for heat shrinkage, the hot melt adhesive 3 leaks out of the heat shrinkable tube 4 while the melted hot melt agent 3′ is cooled and solidified, and the wires W cannot be completely sealed without the hot melt agent 3′ fulfilling its function as the sealing member. Further, if the hot melt agent 3 leaks out of the heat shrinkable tube 4, an operation becomes difficult to conduct for an operator.
The present invention was developed in view of the above problems and an object thereof is to provide a waterproofing method capable of solving the above problems occurring in the case of a using a heat shrinkable tube and having good waterproof performance and high operability while using the heat shrinkable tube filled with a waterproofing agent instead of using a protection cap as a resin molded article.